Typically non-stereoscopic rigid endoscopes feature a single optical path extending from the distal end of the endoscope to the proximal end of the endoscope. The optical system typically includes, from distal end to proximal end, (i) an objective lens, (ii) one or more optical relays, and (iii) an ocular portion. The optical system defines the field of view of the endoscope, which typically ranges from about 60° to about 120°, depending on the types of medical procedures that the endoscope is designed to be used for.
In many circumstances this “instantaneous” field of view is too limited to allow the full operative field to be simultaneously viewed during the medical procedure. As a result, in order to expand the useful field of view, many commercially available endoscopes are designed to have an off-axis direction of view. This off-axis direction of view is achieved by providing a direction-of-view prism in the objective lens portion of the optical system. Typically endoscopes have 30, 45 or 70 degree direction-of-view angles as measured between the direction-of-view axis and the longitudinal axis of the endoscope shaft. Such endoscopes are offered by Karl Storz, Inc., Stryker, Inc., Olympus, Inc. and other manufacturers.
With an off-axis direction of view endoscope, the user can rotate the endoscope about the longitudinal axis of its shaft and effectively expand the “instantaneous” field of view by twice the angle of view value while the endoscope rotates (or “pans”) about a full 360 degrees.
In the case of non-stereoscopic endoscopes, the endoscope is typically rotatably coupled to a video camera. In this situation, in order to expand the “instantaneous” field of view, the user simply axially rotates the endoscope relative to the coupled video camera, which is maintained in a relative “up and down” fixed orientation.
However, with rigid stereoscopic endoscopes, there are typically two parallel optical paths transferring independent optical images to a 3D video camera, where the separate images are received by image sensor(s), converted to electrical signals and further processed in order to be displayed on a 3D viewing device, e.g., a 3D monitor, a 3D head-mounted display or the like.
Due to the stereoscopic requirement for two separate optical paths, it is not possible to simply axially rotate the stereo endoscope relative to the stereo video camera. Thus, for the user to look right, left, up or down, the entire combination of camera and endoscope rotates, causing the displayed image to also rotate, in much the same manner as if one held a photograph in their hands and rotated the entire image. This situation causes significant inconvenience for the physician performing the endoscopic procedure since it becomes difficult to maintain an up-down orientation and goes against common practice developed over the years for non-stereoscopic endoscopy.
Thus there is a need for a new 360 degree panning stereo endoscope which maintains an up-down orientation as the stereo endoscope pans an operative field.